[grivera]

I measured for pushrods this past weekend and came up with an interesting pattern. Because I am using HR lifters, I had to get creative - so used the method Cliff recommends. This involves extending the adjustable pushrod until it bottoms out the lifter, then adjusting accordingly for the best pattern while keeping the lifter bottomed out. Once best pattern is obtained, one subtracts the extra length ( beyond the manufacturer’s recommended preload amount) to come up with proper length. In my case, that length is 9.0375. Using a Comp Cams 7704 adjustable pushrod .
The lifters are Comp Cams Evolution lifters which have .125 of travel and recommended preload is .0625

The cam is an OF1 (236/245, ..627/…632 with Harlan’d Sharp 1.65 rockers.) Valve spring installed height is 1.83”, heads are KRE 310 cfm, originally 85cc, shaved .030 for 81cc.

Following this I contacted JBP for recommendation on pushrods to buy and sent in the pattern. The tech said with 1.65 rockers I can’t go by the sweep pattern and that I should use a 9.2” pushrod. Any thoughts/experiences with this?

Pic attached is the pattern a 9.0375 - the left of the spring is the intake/rocker stud side

[steve25]

I am at a complete loss as to why with any rocker ratio being used you can’t go by the sweep pattern seen.

Maybe the person you spoke to knows that the sharps are much closer to being 1.7 and has seen that length he told you to use work better on average in actual use because that’s the only reason I think of for him to give you that length recommendation.

[grivera]

Here his message:

“With a 1.65 rocker my best guess would be a 9.200” pushrod (there’s more to it than a pattern on the valve tip) The longer rod should bring it slightly back towards center but more important the geometry through out the rocker travel will be much better.”